Semiconductor lasers are used as components in many optical systems. A Vertical Cavity Surface Emitting Laser (VCSEL) is one type of semiconductor laser. Because the VCSEL can be manufactured and tested less expensively than other semiconductor lasers, the VCSEL is often a preferred light source in many applications. Like other semiconductor lasers, however, the output power of a VCSEL changes or varies with temperature and time as the VCSEL ages.
One approach to maintain a steady or constant output power for the VCSEL is to monitor the VCSEL's light output. A portion of the VCSEL's light output is typically diverted in a feedback loop onto a monitoring device, such as a photodiode. When the VCSEL's output power varies, the feedback circuitry adjusts the drive current provided to the VCSEL, which in turn, compensates the output power generated by the VCSEL. A partially transmitting mirror, also known as a window-mirror, is commonly used to divert a portion of the VCSEL light output onto the photodiode.
One prior art technique to monitor the power emitted by a vertical cavity surface emitting laser (VCSEL) is to utilize an external optical surface to split a fraction of the emitted laser power and to re-direct it onto a separate photodetector device. U.S. Pat. No. 6,636,540, entitled “Optical turn for monitoring light from a laser,” describes an example of this approach. Although a significant improvement over the approaches existing at that time, such a solution requires separate optics and detector components to realize the power monitoring.
In most prior art systems, there are at least the following separate components: a VCSEL component, a photo detector component and optics. As can be appreciated, the optical component, laser component, and detector component must be carefully assembled and integrated to produce a working system. Furthermore, it is recognized in the art that integrating the optics component with the other components requires complex system integration. This system integration can include alignment, complicated assembly steps, and packaging methods. Moreover, the number of separate pieces or components undesirably increases the overall package size. Furthermore, different product platforms each require a specific design to integrate the separate optical components, laser component, and detector component.
Based on the foregoing, there remains a need for a system and method for integrating a light emitting device and a power monitor that overcomes the disadvantages set forth previously.